1. Field of the Invention
The present invention relates to a method of fabricating a cylindrical ceramic laminated body which can be used as, for example, a cylindrical ceramic multilayer capacitor.
2. Description of the Prior Art
Fabrication of a cylindrical ceramic multilayer capacitor as an example of a cylindrical ceramic laminated body, has heretofore employed fabricating methods such as spray processes or rolling and isostatic pressing processes.
In the spray process, ceramic slurry is applied to the periphery of a bar-shaped core by spraying and is dried, thereby forming a ceramic layer on the outer surface of the core. The surface of this ceramic layer is then subjected to masking. Next, an electrode paste is applied by means of a spray and is dried. The above described step of applying and drying the ceramic slurry and applying and drying the electrode paste are repeated a plurality of times, thereby to obtain a cylindrical ceramic laminated body having a structure in which electrode paste is arranged between ceramic layers. This cylindrical ceramic laminated body is sintered, thereby allowing a cylindrical ceramic sintered body to be obtained.
The above described spray process has various disadvantages. When the ceramic slurry and the electrode paste are applied by spray, a significant amount of material is scattered to the surroundings. Consequently, large amounts of coating material are required resulting in significant material loss.
Furthermore, when the electrode paste is applied by spray, the electrode paste material adheres to the reverse side of the masked surface. As a result, an electrode having an exact shape is not easily formed. In addition, air becomes trapped between the masked surface and the sprayed paste. Consequently, it is difficult to form elaborate and uniformly thick ceramic and electrode layers.
On the other hand, in the rolling and isostatic pressing process depicted in FIG. 13, ceramic green sheets 17 and 18 having electrodes 15 and 16 printed on one of their surfaces are prepared. As shown in FIG. 13, a plurality of ceramic green sheets 17 and 18 are laminated, to be wound around a bar-shaped core 19. A laminated roll 20 is obtained by this winding. As shown in FIG. 14, the laminated roll 20 is then packed in a resin film under vacuum. The vacuum packed laminated roll 20 is pressurized in a tank for isostatic pressing (not shown). Consequently, the ceramic green sheets 17 and 18 laminated are joined to each other by the applied pressure.
The above described rolling and isostatic pressing process has several disadvantages. The isostatic pressing causes a flow of material. Therefore the laminated roll 20 is liable to be crumpled or deformed around its peripheral surface. Moreover, the shape of the electrode is altered by applying pressure. Accordingly, it is difficult to obtain the desired properties. Furthermore, when a plurality of laminated rolls 20 are formed along the longitudinal direction of a single core 19, as is often done in order to increase productivity, each of the laminated rolls 20 can be deformed if the core 19 is deflected from its original orientation. In addition, the core 19 are projects outward from the inside of the laminated roll 20. Thus, when hydrostatic pressure is increased, a vacuum pack 21 shown in FIG. 14 is capable of being damaged. Consequently, it is difficult to join the ceramic green sheets 17 and 18 to each other by means of strong pressure.